Study On The Oil Phase Of Emulsion Adjuvant For Stable,Safe And Efficient Vaccination

Vaccine is of irreplaceable significance,as a biological product,in preventing and treating diseases.As an important part of vaccines,the addition of adjuvants not only improve the stability of vaccines,but also the effectiveness of vaccines.As the only clinically approved adjuvant for use in vaccines in China,aluminum adjuvant(alum)can enhance the humoral immune response,but it has technical barriers,as it is difficult to manipulate antigen delivery to activate cellular immunity.It is of great significance on the design of new vaccine adjuvants with further stability,safety and efficacy vaccine adjuvants based on aluminum adjuvants for the rapid construction and clinical translation.The particle-stabilised emulsions(Pickering emulsions)with approved aluminum adjuvants and squalene not only increase antibody secretion and dose sparing,offer increased surface areas and cellular interactions for higher antigen loading and enhanced cellular immune responses as well.However,squalene as the only oil phase used in the previous experiments,not only expensive,but also provided limited antioxidant properties,induced harmful substances such as aldehydes and ketones,which will damage the safety and stability of the vaccine.This is not conducive to clinical translation.In response to these challenges,the optimal oils were screened for enhanced emulsion adjuvants based on aluminum-stabilised Pickering emulsions(ASEs).Furthermore,particle-stabilised emulsions with soybean oil,peanut oil and olive oil as the oil phase were constructed,respectively,and stability and immune effect were tested for optimising the oil phases.The specific survey results were as follows:1.Soybean oil,peanut oil and olive oil with increasing oleic acid to linoleic acid ratio and squalene were selected as the oil phase.Aluminium stabilised emulsions,were prepared by one-step ultrasonic.Conducted optimizations included oil phase volume,particle concentrations,buffer types and pH,as well as ultrasonic time,ultrasonic power,ultrasonic temperature and so on,aluminum-stabilised Pickering emulsions droplets with different oil phases were prepared with uniform particle size,similar size(about 1,600.00 ± 71.75 nm)and long stability.2.OVA was selected as the model antigen to evaluate the stability and immunogenicity of aluminum-stabilised Pickering emulsions prepared with different oil phases.On the one hand,this study elucidated the underlying relationship between the oil phase oleic acid to linoleic acid ratio and emulsion stability.The results showed that a higher oleic acid to linoleic acid ratio can increase the antioxidant properties,while decreasing the surface zeta potential to diminish long-term storage stability.The stability of Pickering emulsions prepared with different oil phases was comprehensively evaluated by a Likert scale to quantify the four relatively independent items of aggregation occurrence,size changes,and oxidation induction period.The results showed that aluminum-stabilised Pickering emulsions prepared with squalene or soybean oil as oil phase have excellent comprehensive stability.On the other hand,in vivo and in vitro experiments in animals confirmed that the adsorption efficiency of aluminum-stabilised Pickering emulsions prepared with different oil phases to the antigen was not affected by the composition of the oil phase,but its immune effect was related to the composition of the oil phase.Compared with the aluminumstabilised Pickering emulsions prepared with squalene as the oil phase,the aluminumstabilised Pickering emulsions with soybean oil as the oil phase showed a comparable immune response,while the Pickering emulsion with peanut oil and olive oil as the oil phase showed weaker effect.By optimising the oil phase of the emulsion adjuvants,this work may offer an alternative strategy for safe,stable,and effective emulsion adjuvants.